Prepulse technique for producing low-<i>Z</i>Ne-like x-ray lasers

Nilsen, Joseph; Bj, MacGowan; Lb, Da Silva; Jc, Moreno Giménez

doi:10.1103/physreva.48.4682

Cited by 179 publications

(59 citation statements)

References 13 publications

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“…Ti plasmas have been studied for many reasons including their use as X-ray lasers [24]. Ni-like Pd [25] has been used very successfully as an X-ray laser for many years and currently is used as the laser source for the interferometer measurements at LLNL.…”

Section: Analysis Of Other Plasmas Using Carbon Titanium or Palladiummentioning

confidence: 99%

Impact of anomalous dispersion on the interferometer measurements of plasmas

Nilsen

Johnson

Iglesias

et al. 2006

Journal of Quantitative Spectroscopy and Radiative Transfer

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For many decades optical interferometers have been used to measure the electron density of plasmas. During the last ten years X-ray lasers in the wavelength range 14 to 47 nm have enabled researchers to use interferometers to probe even higher density plasmas. The data analysis assumes that the index of refraction is due only to the free electrons, which makes the index of refraction less than one and the electron density proportional to the number of fringe shifts. Recent experiments in Al plasmas observed plasmas with an index of refraction greater than one and made us question the validity of the usual formula for calculating the index of refraction. Recent calculations showed how the anomalous dispersion from the bound electrons can dominate the index of refraction in many types of plasma and make the index greater than one or enhance the index such that one would greatly overestimate the electron density of the plasma using interferometers. In this work we calculate the index of refraction of C, Al, Ti, and Pd plasmas for photon energies from 0 to 100 eV (12.4 nm) using a new average-atom code. The results show large variations from the free electron approximation under many different plasma conditions. We validate the average-atom code against the more detailed OPAL code for carbon and aluminum plasmas. During the next decade X-ray free electron lasers and other sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential.

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Section: Analysis Of Other Plasmas Using Carbon Titanium or Palladiummentioning

confidence: 99%

Impact of anomalous dispersion on the interferometer measurements of plasmas

Nilsen

Johnson

Iglesias

et al. 2006

Journal of Quantitative Spectroscopy and Radiative Transfer

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“…For the mid-Z Ni-like ion lasers like Pd, this has been recently determined through near-field imaging and x-ray laser interferometry techniques as occurring in the ~ 2 × 10 20 cm -3 region when the plasma density gradients have been relaxed [11]. The use of a prepulse or a long nanosecond pulse to form the plasma followed by a more intense main pulse or picosecond pulse to produce the inversion is important [12,13]. The main disadvantage of the normal incidence pumping is that substantial plasma regions regardless of the net contribution to the inversion have to be heated simultaneously in order to make the laser work.…”

Section: Grazing Incidence Pumping Geometrymentioning

confidence: 99%

Grazing incidence pumping for high efficiency x-ray lasers

2005

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Over the last decade, most laser-driven collisional excitation x-ray lasers have relied on the absorption of the pump energy incident at normal incidence to a pre-formed plasma. The main advantage is that the inversion can be created at various plasma regions in space and time where the amplification and ray propagation processes are best served. The main disadvantage is that different plasma regions regardless of the contribution to the inversion have to be pumped simultaneously in order to make the laser work. This leads to a loss of efficiency. The new scheme of grazing incidence pumping (GRIP) addresses this issue. In essence, a chosen electron density region of a pre-formed plasma column, produced by a longer pulse at normal incidence onto a slab target, is selectively pumped by focusing a short pulse of 100 fs -10 ps duration laser at a determined grazing incidence angle to the target surface. The exact angle is dependent on the pump wavelength and relates to refraction of the drive beam in the plasma. The controlled use of refraction of the pumping laser in the plasma results in several benefits: The pump laser path length is longer and there is an increase in the laser absorption in the gain region for creating a collisional Ni-like ion x-ray laser. There is also an inherent traveling wave, close to c, that increases the overall pumping efficiency. This can lead to a 3 -30 times reduction in the pump energy for mid-Z, sub-20 nm lasers. We report several examples of this new x-ray laser on two different laser systems. The first demonstrates a 10 Hz x-ray laser operating at 18.9 nm pumped with a total of 150 mJ of 800 nm wavelength from a Ti:Sapphire laser. The second case is shown where the COMET laser is used both at 527 nm and 1054 nm wavelength to pump higher Z materials with the goal of extending the wavelength regime of tabletop x-ray lasers below 10 nm.

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“…They include the use of curved laser targets, the reduction of sharp density gradients by the use of a prepulse in laser-pumped systems, [100][101][102][103][104][105][106][107][108][109][110][111][112][113][114][115][116][117] and the use of a magnetic field in dischargepumped lasers. 118 Plasma waveguides having a density minimum on axis have also been developed 74,[119][120][121][122][123] and successfully used in soft x-ray amplification experiments.…”

Section: ͑7͒mentioning

confidence: 99%

Table-top Soft X-Ray Lasers

Rocca

2016

Conference on Lasers and Electro-Optics

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This article reviews the progress in the development of practical table-top sources of soft x-ray laser radiation. The field is rapidly approaching the stage at which soft x-ray lasers sufficiently compact to fit onto a normal optical table will be routinely utilized in science and technology. This is the result of recent advances in the amplification of soft x-ray radiation in both compact laser-pumped and discharge-pumped devices. The use of excitation mechanisms that take full advantage of new ultrafast high power optical laser drivers and multiple pulse excitation schemes has resulted in the demonstration of saturated soft x-ray amplification at wavelengths as short as 14 nm using several Joule of laser-pump energy. Moreover, several schemes have demonstrated significant gain with only a fraction of a Joule of laser-pump energy. In addition, the demonstration of saturated table-top soft x-ray lasers pumped by very compact capillary discharges has shattered the notion that discharge-created plasmas are insufficiently uniform to allow for soft x-ray amplification, opening a route for the development of efficient, high average power soft x-ray lasers. Recently, a table-top capillary discharge laser operating at 46.9 nm has produced millijoule-level laser pulses at a repetition rate of several Hz, with a corresponding spatially coherent average power per unit bandwidth comparable to that of a beam line at a third generation synchrotron facility. This review summarizes fundamental and technical aspects of table-top soft x-ray lasers based on the generation of population inversions in plasmas, and discusses the present status of development of specific laser systems.

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Prepulse technique for producing low-ZNe-like x-ray lasers

Cited by 179 publications

References 13 publications

Impact of anomalous dispersion on the interferometer measurements of plasmas

Impact of anomalous dispersion on the interferometer measurements of plasmas

Grazing incidence pumping for high efficiency x-ray lasers

Table-top Soft X-Ray Lasers

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